Thickened aqueous explosive composition containing entrapped gas



United States Patent 14 Claims. 01. 149-49 ABSTRACT OF THE DISCLOSURE This invention relates to blasting agents and more particularly to slurry blasting agents containing strong oxidizer salt, sensitizer, water, etc. which have air or other gas introduced to reduce density. Organic liquid, e.g., ethylene glycol, formamide, may replace part of the Water to lower its freezing point.

This application is a continuation of application Ser. No. 422,034, filed Dec. 29, 1964, now abandoned, which is a continuation-in-part of application Ser. No. 324,193, filed Nov. 18, 1963 now abandoned.

The term slurry, as employed herein refers to a liquidsolid mixture containing sufiicient liquid to render the liquid phase continuous. Thus, the slurries of this invention have a continuous liquid phase with particulate solids uniformly dispersed therein as distinguished from a mass of wet or moistened solids. The liquid phase may be of any desired viscosity, from thin low viscosity liquids, liquids thickened with colloids, to gelled liquids. In the latter case, the gelatinous phase must be essentially continuous in order to fall within the above definition of a slurry.

A slurry within the above definition theoretically should have a density determined by the densities of the individual solid and liquid constituents and the relative proportions of such constituents. In practice, however, it is difiicult if not impossible to achieve the theoretical density, particularly in slurries of high viscosity or gelled slurries, because of air entrapment. It has been found, however, that lowering of the density by air entrapment to up to twenty-five percent of the theoretical density still produces slurries Within the above definition having essentially continuous liquid phases. The density of a given slurry, therefore, is a measure of the air entrapment therein and hence is a criterion for the continuity of the liquid phase. Thus, a composition which has a density lower than seventy-five percent of the theoretical density is not a slurry within the definition intended herein because the liquid phase is not essentially continuous. 55

Aqueous slurry blasting agents comprising Water, oxidizer and solid sensitizer as described and claimed in Cook and Farnam US. Patent 2,930,685 have enjoyed wide commercial use. As disclosed in Patent 2,930,685, the slurries contained from 5 to 30% Water by weight. It 0 has been found however that it is diflicult to achieve true slurries within the definition at lower Water contents, in the range of 5 to unless the water used in the composition was hot. Thus, compositions according to the Cook and Farnam patent containing as little as 5% water 65 at room temperature are not pumpable and are not slurries under the definition.

The minimum sensitizer content of the Cook and Farnam slurries is about coarse TNT (trinitrotoluene) in order to yield blasting agents of adequate sensitivity to be commercially useful. With single base smoke- 3,382,117 Patented May 7, 1968 less powder, on the other hand, it has been found that a minimum of about is required to yield a true slurry which is sensitive enough to be commercially practical and detonable by low cost boosters. Similarly such smokeless powder slurries required a minimum of about 11% water to yield true slurries.

It is an object of this invention to provide slurry blasting agents containing less explosive ensitizer than prior art compositions and which are more economical than prior art compositions.

It is a further object of this invention to provide blasting agents which posses superior properties including high density, high bulk strength, water resistance, freeze resistance and high sensitivity.

Further objects and advantages will be apparent to those skilled in the art.

According to this invention, true aqueous slurries are provided which have densities of at least 1.3 grams/cc., when free of air or other entrapped gases, and which contain less than 5% by weight of water. The slurries have high bulk strength and are sensitive enough to be detonate-d by inexpensive boosters. The liquid phase in such improved slurries comprises less than 5% by weight of water plus one or more water-soluble polar at least organic substances to form a solvent capable of dissolving approximately its own weight of inorganic oxidizer salt at ambient temperatures. The oxidizer salts useable in the slurries of the invention include ammonium nitrate, sodium nitrate, barium nitrate, or mixtures thereof, the preferred oxidizer being ammonium nitrate. The polar organic materials include alchohols such as isopropyl alcohol; polyhydric alcohols such as ethylene glycol, diethylene glycol, glycerol; sugars such as sucrose, maltose, dextrose; amides such as formamide, acetamide, urea; and amines such as guanidine and dicyandiamine.

The slurries of this invention preferably contain from about 2 to 4.5% by weight of water and 8 to 14% by weight of polar organic substance.

The sensitizer for the slurry explosives may comprise coarse TNT, or any of the tols including composition B (RDX/TNT/wax), pentolites (PETN/TNT), Ednatols (EDNA/TNT), etc. Composition B is a mixture of cyclotriniethylenetrinitramine (sometimes called cyclonite), trinitrotoluene, and Wax. Pentolites are mixtures of pentaerythritol titranitrate and trinitrotoluene in various proportions, Ednatols are mixtures of ethylene dinitramine and trinitrotoluene. It may also comprise smokeless powder of the single, double and triple-base varieties. The single base smokeless powders contain predominately nitrocellulose; the double-base smokeless powder propellants contain also nitroglycerine, but are still predominantly nitrocellulose. The triple-base smokeless powders contain, in addition to nitroglycerine and nitrocellulose, an insoluble solid explosive. For example, the flashless (triple base) propellant type designated in the U8. military publications as M15 contains about 55% nitroguanidine together with nitrocotton/nitroglycerine in the ratio of 20/19. Other triple base smokeless powders contain in addition to nitrocellulose and nitroglycerine such explosives as RDX and HMX (hexamethylenetetramine). Slurry explosives made according to this invention may be sensitized also with aluminium or other heat producing metals such as magnesium. The sensitizer may also be any of the high strength, granular explosives including nitrostarch, PETN, RDX, tetryl (ethylenediaminedinitrate), Haleite (trinitrophenylmethylnitramine), or it may be one of the propellants known as composite propellants formulated into granular form, preferably in the range of particle size from min-us 4 to plus mesh although other formulations may be used, though sometimes less effective. The sensitizer may also comprise any suitable combination of these substances.

The liquid phase of the slurry explosives of this invention may be regulated as to viscosity by the use of various hydrophilic colloids including the guar gu-ms, the water soluble carboxymethyl cellulose substances, starch, and

Realizing from these examples that a solvent comprising less than 5% water together with a certain amount of organic material soluble in water as described above may be used to act to produce slurry explosives of equal or other suitable hydrophilic colloids. The thickened liquid 5 better sensitivity and gelation properties than the original phase may likewise be gelatinized by the use of a suitable all water-solvent slurries, it becomes important to detercross-linking agent such as borax in the case of guar gum. mine the x and y values (organic solvent=x percent and Such thickeners or gelling agents are present in amounts water=y percent) necessary to obtain suitable slurries. of 0.2 to 5% by weight. Some observations of the approximate minimum values In the following examples, all percentages and parts of x for a given y are summarized in Table III. are by weight of the total slurry composition. TABLE III A roximate organic solvent re uircment (x) and water re uiremcnt; EXAMPLE I pp (y) for high density lurry explosive formulation] To show the relative merits of slurry'explosives made according to this invention with those of prior art, the Swen x Y solvent X y results shown in Table I were obtained using the comr o Positiom TNT14%, ammonium i t Sodium iitiliit iytaiii 318 iii ififititil tnai: 3:3 1:2 nitrate-40%, sulfur-2.0%, cross-linking borated guar Glycerine 9.0 4.5 Polysolvent 9.0 4.5 gum-0.5%, water4.5% and organic 1iquid10%. Gimme These were compared with a standard slurry prepared according to Patent 2,930,685 containing 16% TNT, 59% In order to determine the minimum water requirement, ammonium nitrate, 8% sodium nitrate, 2% sulfur, 0.5% several slurries were made using the general composition cross-linking borated guar gum and 14.5% water. In all shown in Example II except that the x and y values were cases the TNT was minus 4 to plus 20 mesh particle size. varied. Using either formamide or ethylene glycol it was TABLE I Organic Liquid Standard Isopropyl Formamide Ethylene Glycerine Alcohol glycol Percent organic N one 10 10 10 10 Percent water 14.5 4.5 4.5 4.5 4.5 Slurry density (g./cc.) 1. 38 1.38 1. 34 1.30 1. 89 Critical Diameter unconfined using 380 g. cast pentolite booster (in) 6 6 4 4 4 While the shlrry made With P PY was no 35 found that slurries were inferior and required excessive better than the standard, there was a substantial improveorganic liquid when no water at all was used; the .best mellt 1I1 $BI1S1[1V1W resulhhg by the shbshtuhoh of 10% results were obtained in both cases by the use of about 2 formamlde, ethylene g y 0r y for 1 of h to 3 parts water in conjunction with these solvents. Thus, 14.5% water. Furthermore, the slurries with organic A at and 36:95 for formamide the critical diameter additives were lower in freezing point and provided better 40 was at a density of 1.36 gjee The density was Swelling of the guar They also had better Water creased to 1.45 g./cc. by increasing the formamide by sistance than the standard water slurry. Moreover, the only Two three parts more ethylene glycol were TNT slurry explosives of prior art were found to require required to Obtain a good high density Slurry than when about 5% more TNT to sensitize them to the same level formannde was used in mixtures with 2 to 3% water as that of the Shlmes Inflde Wlth 10% formamlde, and Various combinations of formamide with glycerine, ethylene glycol glyceflheethylene glycol and sugar, and ethylene glycol and molas- EXAMPLE I1 ses were studied with essentially the same results. For example, a 5/ 5/ 4.5 mixture of formamide/glycerine/water lanolher gf i. thg i' 75 t i gave a slurry explosive of 4" critical diameter at 1.3 6 5. 27 'i i g./cc., slightly more liquid phase being needed to obtain par so i ii g i; Su a a density in the range 1.45 to 1.5 g./cc. A mixture of Parts Cross-H, a 10 parts of 7/3/4.5 formamide/sugar/water yielded a x parts organic liquid was studled with the following slurry having a density of 146 and having a Sensitivity results comparable to those of the prior art slurries.

TABLE II The slurries of the invention thus comprise compositions in which the water content is from 2 to 4.5%, polar rga i Additiv F rm d pg d l F rm m d organic material 8 to 14%, sensitizer 8 to 30% and the i i remainder oxidizer and thickeners, all by weight. Pre- Parts (0 10 10 9 5 ferred amounts of sensitizer are 10 to 25% for TNT, 15 w {5;1;-3jjjj 1 o 0% for smokeless powder, and /2 to 20% for par- 1 e it g;./ee 1. 4s 1. 46 1.36 ticulate aluminum.

5 5 5 Thus, the slurries of this invention possess sensitivities equal to or greater than those of the prior art while utiliz- TABLE IIA ing smaller amounts of the sensitizer, which is the most Organic Additive Formamido Glycerine Ethylene expensive mgredlent emPloyed the FQ P Glycol cause they are true slurr1es having dens1t1es of 1.3 g./ cc. 10 n) 10 and higher when free of air or other entrapped gases, they 4. 5 4. 2 4.3 possess high bulk strength. Additionally, the water re- (unconfined) 6 sistance and antifreeze properties of the slurries are greater (in) 5 5 5 7 than those of the prior art.

In most cases these improved slurry explosives appeared to be better in sensitivity, plasticity, swelling of the gum and freezing point than the corresponding slurries using all water as the solvent.

While the minimum density of the slurries of this invention when free of entrapped gases is 1.3 g./cc., air entrapment produced in the mixing of thickened slurries may reduce the density up to 25% of this value. Thus, such thickened, air-containing slurries having densities of 1.0 g./c-c. or slightly lower have been found to be operable and are within the scope of this invention.

It is to be understood that the definition of slurries as used herein applies to the state of the material as it is mixed. Thus, slurry blasting agents may be prepared at elevated temperatures which facilitates the mixing operation. Upon introduction into the bore hole, such hot slurries will cool and the resulting product may not be a true slurry, because of crystallization of ammonium nitrate, etc. However, it is intended to cover slurries within the definition as mixed.

While the invention has been described in terms of certain examples, they are to be considered illustrative rather than limiting and it is intended to cover all further modifications and embodiments that fall within the spirit and scope of the appended claims.

What is claimed is:

1. A pumpable aqueous explosive slurry blasting composition, which comprises a major proportion of inorganic oxidizer salt, /2 to 30 percent of a sensitizer selected from the group which consists of particulate trinitrotoluene, smokeless powder, mixtures of cyclonite-trinitrotoluene-wax, mixtures of trinitrotoluene-pentacrythritoltetranitrate, trinitrotoluene-ethylenedinitramine mixtures, nitrostarch, pentaeiythritoltetranitrate, cyclonite, trinitrophenylmethylnitramine, ethylenediaminedinitrate, aluminum and magnesium, and mixtures thereof, a liquid in proportions sufficient to form a substantially continuous phase and consisting of water and a water soluble polar substance selected from the group which consists of alcohols, polyhydric alcohols, sugars, amides and amines, the composite liquid being capable of dissolving at least approximately its own weight of the inorganic oxidizer salt at ambient temperatures, and a thickener for said slurry to inhibit segregation of said particulate matter from the suspending liquid, said blasting composition having a density of at least 1.3 grams per cubic centimeter when free of entrapped gases.

2. Composition according to claim 1 wherein there is included sufiicient entrapped gas to lower the density up to 25 percent.

3. Composition according to claim 1 wherein the sensitizer comprises TNT.

4. Composition according to claim 1 wherein the sensitizer comprises aluminum particles.

5. Composition according to claim 1 wherein the sensitizer comprises smokeless powder.

6. Composition according to claim 1 wherein the oxidizer salt consists essentially of ammonium nitrate and sodium nitrate, wherein the sensitizer comprises aluminum, and wherein the overall density of the composition is reduced up to 25 percent by inclusion of the entrapped gases.

7. Composition according to claim 1 wherein the polar organic compound comprises ethylene glycol and wherein a guar gum is included as a thickener.

8. Composition according to claim 7 wherein a crosslinking agent is included.

9. Composition according to claim 1 wherein formamide is included in the liquid.

10. Composition according to claim 1 wherein the oxidizer salt comprises 53 to 69 percent, by weight of the total composition, of a combination of a major amount of ammonium nitrate and a minor amount of sodium nitrate.

11. Composition according to claim 10 which also includes sulfur.

12. Composition according to claim 1 which contains less than 5 percent water.

13. An inorganic oxidizer salt type blasting composition formed by admixing water, an inorganic oxidizer salt, a sensitizer, a thickener, and a gas to form a blasting composition of aqueous slurry type, said resulting slurry containing said gas in an amount suflicient to cause a predetermined lowering of the density of said slurry.

14. A blasting composition according to claim 13 wherein the gas is air incorporated in proportions such as to lower the density of said composition up to 25 percent.

References Cited UNITED STATES PATENTS 1,186,065 6/1916 Aubert et al. 14918 2,768,072 10/1956 Stark 149-2 X 3,004,842 10/1961 Rowlinson 14957 X 3,049,454 8/1962 Stark 149-2 3,201,291 8/1965 Schmidt 14944 X 3,202,556 8/1965 Chrisp 14957 X 3,212,944 10/1965 Lyon et al. 149-46 X 3,247,033 4/1966 Gordon 14918 3,249,474 5/1966 Clay et al. 149-41 X 3,282,752 11/1966 Clay et al. 14922 X 3,288,658 11/1966 Ferguson et al 149-61 X CARL D. QUARFORTH, Primary Examiner.

BENJAMIN R. PADGETT, Examiner.

S. I. LECHERT, JR., Assistant Examiner. 

